Into The Nightosphere
by Cardinia
Summary: Several years have passed since we last saw AAA's heroine and now the young adventuress is on the cusp of her 18th birthday. But with mass monster summonings, old flames and one particularly attractive vamp, will Fionna be able to make it to her birthday in one piece? Sequel to the short story 'For Every Piece of Me'. Fiolee Lemon (with plot!)
1. Summoning Problems

**You don't need to have read my short oneshot 'Every Piece of Me' before reading this, but if you are interested then it's a little meeting between Marshall and Fionna a few years before the start of this one.**

 **Reviews would be fantastic. If you spot any details I've gotten wrong or have any suggestions in terms of writing I'll be more than happy to hear them.**

 **Just to let you guys know, this fic is set in the same universe as the Fionna and Cake comic book. If you haven't read it I suggest you go out and buy a copy; it's awesome. But some details of the story may seem weird if you haven't read that AND there will be spoilers. Fair warning has been issued!**

 **Here's the obligatory spiel of I DON'T OWN ANYTHING.**

 **Enjoy!**

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Lightning tore through the sky and illuminated the horde of blood thirsty monstrosities that charged across the sand. A lone adventuress raised her sword in the air and let loose a battle cry that rivalled the rolling thunder before charging into the fray and hacking at the many-tentacled beasts. A mixture of sweat, raindrops and sea water slathered her body as Fionna slashed through her enemies whilst dodging their sharp teeth and prolific suckers. With a yell she jumped before pivoting mid-air and slicing the head of one particularly nasty specimen that had just been about to wrap it's fore-tentacle around her waist. She rolled as she hit the ground and was about to spring back up when one of the monster caught her face and pinned her back to the ground. She grunted and barely managed to free herself in time before the creature's great jaw snapped at the space where her head had been. With a roll of her eyes Fionna pushed herself up and cracked the butt of her sword against the monster's teeth, revelling in the scream of pain it released as it's canines cracked off into the ground. Laughing, the young woman rolled her shoulders and looked out towards the rest of the horde. Her eye spied a glowing stone nestled between some rocks and shells at the edge of the water, it's light almost obscured by the rolling mass of creatures. Fionna's eyes narrowed at the sight of the summoning stone and a deadly smile played across her lips. "Gotcha" she whispered whilst absentmindedly dismembering yet another beast, before taking off towards the source of this afternoon's trouble.

* * *

By the time Fionna Merten's made it back to her treehouse home she was in a pretty foul temper. If it was anyone else, one could have been forgiven for thinking it was the sheets of rain that had soaked the girl to the bone, or perhaps the cuts, bruises and burns that caused her anger. But Fionna was used to this sort of treatment and had held the title of Aaa's defender since the tender age of 13. No, the reason for her ire today was clenched in one bloodied hand whilst the other grasped the hilt of her once very sharp, now very blunt sword. With a weary sigh she pushed open the door to her home and climbed the ladder to her living room. She immediately made a beeline for her couch and sank into it with a grateful moan before putting her feet up on the coffee table. After the afternoon's antics she was more than ready for a little rest and relaxation.

"Fionna! Sweet babies girl look at the state of you!" Cake's shriek cut through the air and attacked Fionna's eardrums with all the sensitivity of a battle-axe to the face. Fionna winced and cracked open one eye to see her sister's face looming over hers, and surprise surprise, the cat looked pissed off.

"Cake just gimme a minute kay? I've had a reaaaally long day." Fionna went to shut her eye but swiftly realised that her sister had other ideas.

"A long day? A LONG DAY FIONNA?!" Cake malleable form grew bigger and bigger with each word until she was towering above her sister. With her fur angrily sticking on end she resembled an angry bear and the petite blonde opened both eyes before sitting up slightly straighter and sighing.

"Okay okay, I'm sorry alight? I didn't think it was gonna be so bad Cakey. It was only a litt-" Fionna's words were cut off by an angry hiss and she re-assessed her idea to use her sister's pet name. Sometimes it paid off, but other times it made the situation ten times worse. She winced inside as she realised this was one of the latter times.

"Fionna I can't believe how reckless you were. We are a team. A. TEAM. That means you don't go running off on your own to Glob knows where to fight Glob knows how many monsters all by yourself." Cake's scowl softened slightly as she took in the sight of her little sister, assessing the sheer number of wounds she had on her tanned skin. "Fionna…" She lowered her voice along with her size and crawled onto the sofa before wrapping her arms round the young woman. "Look at you. I mean, have you even seen yourself? You had me so scared." The cat nestled her head into Fionna's shoulder and tightened the hug enough to make the girl wince.

"Oh Cake… I'm sorry. But you were out with LM and the kids when the call came in. I didn't want to bother you. Anyway, I'm fine. Nothing some sleep and bandages won't fix." She smiled at her sister and breathed a small sigh of relief as Cake smiled back and the two hugged for a little longer on the sofa.

Once Fionna had drifted off to sleep Cake unwound her arms from the girl and leaned back with a sigh whilst rubbing her tables with two forefingers. The young adventuress had grown considerably in the last few years and Cake almost burst at the seams with pride whenever she saw her taking down a monster or practicing with her sword and bow. Still, the years of fighting hadn't left Fionna completely unscathed and Cake knew her body was littered with small scars and reminders of past battles. Cake smiled sadly as she gazed at her sleeping sister's angelic face and came to the conclusion (as she had many times before after worrying herself witless over the girl), that Fionna just wouldn't be happy if she wasn't out fighting demons or saving princes. The cat went to bustle away and fetch the first aid kit when she noticed a dull glow emanating out of one of Fionna's clenched fists. Even in sleep the adventuress clung onto the item tightly and it was no small feat for Cake to pry her hand open to retrieve the bauble without waking the girl up.

Cake's pupils widened at the sight of the rock and a small hiss escaped her teeth. The summoning stone had a crack straight down the middle, no doubt put there by Fionna's sword, but it still emitted a faint blue glow that would have been entrancing if Cake hadn't known the vile nature of the ornament. Summoning stones were used by witches, wizards and demons to call forth great armies of monsters to do their bidding. If Cake hadn't been so worried about Fionna getting some sleep she would have woken her up to demand details of just how bad this afternoon's fight had been. As it was she simply hissed and created a small pocket to place the stone into. Summoning stones weren't particularly rare but they weren't common either, and this was the sixth one to turn up in the past 8 months. Cake's nose twitched as she decided that something definitely smelled fishy, and it wasn't just Fionna's unwashed socks this time.

* * *

The late afternoon soon turned into night, and with it went the bad weather. Cake had cleaned Fionna up as best she could while she slept and had moved her to their shared bedroom so she could get some proper rest. Now the cat lay in the little boat on top of the treehouse alongside BMO as they pointed out constellations in the sky.

"Ooh, I think that one my favourite." The little bot cried as Cake pointed out Ursine Major (the great bear-horse) and the two giggled away to themselves. When Cake had caught her breath she rolled over to BMO and tapped her nose with one sharp claw.

"Hey BMO, I've been thinkin'. We need to do something for Fionna to cheer her up. Something that doesn't involve fighting!" BMO nodded solemnly and the two pondered for a while as they lay there.

"I have got it!" The robot shouted and she waved her two arms in the air in a little dance. "We could make her a pretty necklace from the stones she finds. All women like necklaces." BMO's arms stopped their waving as she saw Cake shake her head.

"Those aren't just pretty stones sugar plum. Those are summoning stones and they're crazy nasty. That's why we need to cheer her up, she's been running around all over the place tryna find who keeps leaving them out but all she's done is give herself a headache." The cat resumed her nose tapping until she leapt up with a shriek that had BMO falling over in fright. "AHA! I've got it. Oh this'll be so perfect, she won't know what's hit her!"


	2. Best Laid Plans

**Chapter 2 - Best Laid Plans.**

 **So it's early days yet but let me know what you of the chapter lengths so far. I think they may be a little too short but yeah, let me know.**  
 **Of course I don't own the characters, and R &R is always appreciated :)**

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A soft summer breeze played with the branches of the treehouse, giving no indication of the stormy weather the day before. Small flowers bloomed around the doorstep and the sweet smell of flora filled the air. All was peaceful and quiet in the idyllic scene until a raging scream split through the air. Birds flew squawking from the trees and a stray axe flew through the a window to land directly in the well tended flowerbeds.

"Sweet babies! My flowers." The white and tan cat threw open the door to look at her plants sadly. "Fionna you gunked up ma flower beds!" Cake humphed and picked up the axe with an enlarged hand. Throwing the offending weapon into the field she ignored an annoyed "hey!" from a family of dormice she had disturbed and set about attempting to prop up the broken stems. Every time she removed her paws from the flowers they flopped back down. With a yell of frustration Cake swiped the heads off of the flowers with her sharp claws. "Fionna! Fionnaaaaaaa!" With each swipe her annoyed cries got louder until she saw a familiar blonde head poke out the window above.

"Cake, whaddya want?" The bedraggled teenager looked down with a questioning frown until she saw the ruined flower patch her axe had so rudely flattened. "Oh Cake… I'm so sorry." She vaulted out of the window in one fluid movement and landed on a forward roll before wincing at her battered body's reaction.

"Well it's no good saying sorry now Fionna." Cake's tail swished the flower debris as she spoke "Ma flowers are all junked up now anyways." She fixed Fionna with a stare and watched as the younger girl seemed to shrink in on herself. "And what are you doing out of bed so soon? You're meant to be resting!"

"Ah I'm sorry Cakey, I was just practicing my swing and I missed the target. And I know I'm meant to be resting… I just wanted to get a little practice in." She had gathered her sister up in a hug as she spoke and rubbed her hair in the cat's soft fur. Cake rolled her eyes as her anger dissipated and returned the hug with a big smile.

"Well never mind now. I was waiting for you to get up anyway." The cat ushered Fionna back into the house and began to talk animatedly whilst redressing the girls wounds. "Now honey I know you've been feelin' down about all these monster attacks lately. So BMO and I have decided to throw you a big birthday party next week!" Cake tightly re-wound the bandages on Fionna's arm and seemed completely oblivious to the girl's look of horror. "It'll be so good sweet buns, we're gonna invite all of your friends and have a whole day filled with no drama, no fights and absolutely NO monsters." It was only at this moment that Cake took a proper look at Fionna's face and the mounting anxiety displayed there. "Well what's wrong honey? Don't you like the idea?"

"It's not that I don't appreciate it, but really? The kingdoms are being plagued with monster problems and you're thinking of throwing me a party? What happens if another stone turns up or a monster crashes it. And plus… what if… what if no one wants to come?" Fionna blushed scarlet and fiddled with the ends of her hair as she said this, her heart pounding with embarrassment. Cake bit back her first thought and studied her sister, she forgot sometimes just how young Fionna was and whilst she may be fearless on the battlefield she had insecurities just the same as any other teenager albeit in slightly ways.

"Don't you worry kitten. You deserve a day off now and again and everyone will want to come to your party. The only reason I was annoyed about the flowers is because I want to get the place pretty for your birthday party. It'll be your big day sweet buns." Fionna was still gazing despondently at the floor so Cake harrumphed and swatted the girl's arm with a paw armed with sharp claws. "Now that's enough of that pity party! You listen here, we're gonna have this party and it's gonna be the best. I spent all night making invitations for you to deliver today. And I don't wanna here any more talk of no partying. It's your 18 birthday which makes this is a Big Deal. With both capitals! It's only a week away and this cat wants to get her booty shaking on down to the sweet tunes of your birthday beats!"

* * *

A little while later Fionna was in her room assessing the plans for the day. Her cuts and bruises had been lovingly (if somewhat forcefully) tended to by her sister and she was sporting a ridiculous amount of plasters and bandages across her arms, legs and even some near her nether regions. Cake had handed Fionna the bundle of hastily made invites and the girl cast a wary eye over them with a sigh before sitting cross legged on the bd and leafing through them. How Cake and BMO had managed to make all these in one night Fionna couldn't guess but it seemed no one had been left out, top of the pile was an invite addressed to one Prince Bubblegum and thereafter one for each of the princes from the various kingdoms. The young woman's cheeks had blushed pink at the sight of PB's name but she had hastily flipped through stack before she could dwell for too long on her longtime candy coated crush. Fionna continued rifling through the invites and smiled occasionally at memories the names incited. It wasn't till she got to the last two that the faint blush in her cheeks re-appeared and then grew till her face felt like it was on fire. The last two invites had been addressed in Cake's delicate scrawl to Flame Prince and Marshall Lee. Placing the rest of the stack on her bed, Fionna took a deep breath before tracing Marshall Lee's name on the top of the invite. She and her old friend had fallen out of contact a few years back after a particularly heated argument, and despite small efforts made from the both of them they had lost the friendship that Fionna had held so dear. As for the other invite, last time she had seen Flame Prince had been years before, when she had saved him and his pride of Fire Lions from the Ice Queen's clutches. Running her hands over her face and letting out a groan Fionna swept the envelopes up and hastily shoved them in with the others before turning her attention to her backpack. Next to actual adventuring and practicing with weaponry her favourite pastime nowadays was to catalogue her gear and keep it clean and sharp, just in case a new enemy appeared on the horizon. With practiced movement Fionna dumped out the contents of her backpack and laid the items out on her bed before picking up a whetstone and damp cloth. She had yet to find a sword that was _the one_ , but she owned a variety of useful daggers and short-swords that had saved her bacon more than once over the years and she picked up a particularly gruesome looking blade and proceeded to sharpen the edge with her stone. She soon feel into a relaxing rhythm and the acidic sound of the whetstone against the blade blended into the background as her mind wandered.

Since the disappearance of the Ice Queen so many years ago the adventuring had been a little on the slow side, with the summoning stone incidents being the only real adventures Fionna had tackled. Nowadays the main events that kept her occupied were royal warrants and helping the various villages that were dotted around the land of AAA with menial tasks. Only last week she had gotten excited at the prospect of helping Slime Prince defeat a great beast that had beset his kingdom, only to find out that the 'great beast' was in fact LSP in disguise looking for free food. With a sigh she set down the throwing dagger she had finished sharpening and reached over to pick up the muddied axe that had fallen in the flowerbeds earlier that day. Just as she set the axe on her lap and picked up a cleaning cloth, her communications device went off. The device itself was bubblegum pink and studded with chocolate chips in the shape of hearts. Sweet as it had been for PB to bake up this particular science gizmo, Fionna always felt slightly nauseated after she used it. And also very sticky. She reached over and jammed a thumb into the candy corn answer button and PB's face appeared above the device in a pink washed holographic image.

"Fionna! Thank glob I've reached you. We have an emergency here at the castle and I need your help right away." Before Fionna had a chance to reply the image cut out and she was left staring at empty space. A slow grin emerged on the girl's face and with an excited yell she leapt off the bed (the axe falling unnoticed to the floor as she did so) and grabbed her newly packed backpack and a fearsomely sharp sword she had nicknamed 'shiny stick' before barreling down the ladder to the living room.

"Cakey we gotta go!" Cried Fionna with a grin still plastered on her face. She was practically hopping from foot to foot she was so excited, and she swept the protesting cat up as she dashed towards the door. "It sounds like something's super crunked up at the Candy Kingdom. Sorry but I think someone else will have to take the invites around! Such a shame but there's no rest for the wicked eh?" Cake looked as if she was about to argue but instead shrunk until she slipped out of the eager girl's arms.

"Okay honey, lemme just grab something. You go on ahead, I'll meet you there!" Cake forced smile stayed in place until the girl was a fair distance away and her smile turned into a frown. "Oh no she doesn't." The cat humphed to herself and leisurely strolled back into the treehouse.


End file.
